Test Match Special analysis

On another miserable day for the tourists, who were bowled out for 128 on Friday to concede a 233-run first-innings lead, Bell was controversially given not out on three by third umpire Tony Hill despite appearing to be caught just above the ground by Steve Smith.

He took full advantage, unfurling some sublime shots after tea and marching towards his third consecutive century of the series, before dragging a long-hop from Smith straight to midwicket.

But, having had a lucky escape on eight on Friday evening when he edged between wicketkeeper and slip, he struck the first ball of the day through midwicket for four and looked untroubled thereafter.

Grinding Australia down

The highest target England have set Australia in an Ashes Test is 742 at Brisbane in 1928. England won by 675 runs as Australia were bowled out for 66.

He took 122 balls to reach his fifty, another 125 to complete a century, but only 64 more to reach 150 as he and Bell carried England's lead beyond 500 to suck any remaining morale out of Australia.

With England's lead already 148 runs in excess of the highest successful fourth-innings chase in Test history, captain Alastair Cook must decide whether to declare overnight and give himself two full days to bowl Australia out, or to continue batting in order to further wear down the pitch.

Either way, with off-spinner Graeme Swann looking to add to his first-innings five-wicket haul on a pitch turning substantially, England appear all but certain to take a 2-0 lead in the five-match series and establish themselves as overwhelming favourites to retain the Ashes.

Australia began the day knowing they needed to pick up where they left off on Friday, when three quick wickets had given them hope of fighting their way back into the game.

They found stubborn resistance, however, as Root and Bresnan carefully consolidated England's overall position of strength during only the third wicketless session of the series.

Test Match Special analysis

"It was a horror day for Australia, probably even worse than Friday. England saw them off early on and then the runs starting to tick over as the day wore on.

"I am curious why Australia didn't take the new ball, run in hard and have a red-hot go at England to show they won't lie down. It became too easy at times.

"Nothing shy of a miracle can save them from here."

Bresnan had advanced to 38, with four fours, when he pulled James Pattinson to midwicket to give Australia their first wicket of the day.

And when Bell appeared to be caught by Smith at gully after fending off a rising delivery from Ryan Harris, Australia thought they had a second.

Bell shrugged to suggest he was unsure whether the catch was clean, and the on-field umpires referred the decision to Hill, who ruled that there was insufficient evidence to give the batsman out.

Australia's players made their frustrations clear to the officials, while an angry tweet containing expletives was posted on the official account of Cricket Australia, prompting an apology from the governing body.

Bell, who scored 109 in both the second innings at Trent Bridge and first at Lord's, showed no remorse as he cut, drove and swept his way to a 36th Test fifty.

He and Root scored 109 in 17 overs either side of tea as England took advantage of some average bowling with the old ball.

Bell sank to his knees in frustration after picking out Chris Rogers to deny himself another hundred, but the day belonged to Root, who signed off in style by launching Smith for two sixes in three balls.